Recently, on my 99 Civic EX I've replaced the exhaust from the
catylitic converter onward and also replaced all of the exhaust gaskets
and nuts/bolts, etc.  During this unlikely hellish event I had to
resort to a hacksaw and a hammer to free several bolts, the worst of
which were the pre-cat. bolts.  My engine light came on the next day.

As a consequence of my methods, I nicked one of the wires going to the
pre-cat O2 sensor, forgot to tape it up and drove for a couple weeks.
When re-fueling, I noticed my gas mileage dropped from 38mph to 22mph.
Thought it was a fluke, drove another week, filled up and calculated
the same milage.  (Yeah, not too smart to drive it under these
conditions, but I had back problems that arose because I'd spent all of
a Saturday under the car trying to fix it, that prevented me from
getting under it again.)

I then patched up the wire (it was only a nick) and searched for any
other problems.  Everything looked fine.  I then reset the engine code
by unplugging the negative battery terminal.

Still same mileage and the light re-appeared.  Now I assume, with all
that banging going on I probably ruined my pre-cat O2 sensor (It's 120K
old anyways).  To be sure, I jumped the wire connections to read the
code and only got a
blink.............blink.............blink......etc...  I watched it
until it consistantly and equally until it blinked 65 times.  No short
blinks, no fast ones, just a constantly slow blink every 3 seconds or
so.

What's this tell me?

P.S.  I am aware that if it is the O2 sensor and I continue to run the
car this fuel rich I will plug the catylitic converter.  I have been
trying to avoid driving the car since this problem has come about.  I
just don't want to buy a $185 sensor until I'm damn sure.

Any ideas?,
John